Before we get to the instructions, it's important to understand the difference between these - an explanation of the difference can be found here.
If you've created two accounts (i.e. registered twice on IMDb with two different emails), see this help article about how to handle.
Instructions
Name Merges can be used to combine entries for a single person that appear under two or more different names. In this case, you should decide which name should remain -- usually the name used most often, though if a person is expected to use a single name for all future credits, this would be the one to choose. If you're confident two pages should be merged together, take a look at the written instructions below.
Step by step instructionsPlease note that the updates may happen in stages, which can mean that some credits may disappear for a day or two while the merge is being processed.
You may also want to review our name submission guide.